Many commercial passenger aircraft use bypass gas turbine engines for propulsion. In a bypass turbine engine, ambient air enters an engine inlet and is pressurized and accelerated rearwardly by a fan located near the inlet. A relatively small portion of the pressurized air from the fan is passed into a core engine where the air is mixed with fuel and ignited causing combustion and expansion of the fuel-air mixture. The expansion of the fuel-air mixture rotatably drives the fan. The discharge of the combustion gas from the exhaust nozzle adds to the propulsive thrust of the gas turbine engine. A relatively large portion of the pressurized air from the fan passes through a fan duct that surrounds the core engine. The air exiting the fan duct may provide a significant portion of the propulsive thrust of the gas turbine engine.
In certain bypass turbine engines such as those having thrust reversers, the fan duct is bifurcated or divided by a pair of inner walls into two semi-circular fan ducts. Each one of the inner walls may include a semi-circular barrel portion that generally surrounds the core engine. The inner wall may also include an upper wall portion and a lower wall portion extending radially from circumferential ends of the barrel portion. The upper and lower wall portion may be coupled to diametrically-opposite sides (e.g., upper and lower sides) of a fan duct outer wall (e.g., a fan reverser cowl). The bifurcated fan duct arrangement provides improved accessibility to the engine interior for inspection and maintenance.
The operating efficiency and performance of a gas turbine engine may be enhanced by improving the aerodynamics of the airflow through the fan duct. For example, the fuel efficiency of a gas turbine engine may be improved by minimizing or eliminating protrusions in the wetted airflow surface of the fan duct. In addition, the specific performance of the gas turbine engine may be improved by minimizing the weight of the engine components such as the weight of the fan duct inner walls and outer walls. Furthermore, the noise output of a gas turbine engine may be reduced by acoustically treating the wetted surface area of the fan duct that is exposed to the airflow.
In view of the foregoing, there exists a need in the art for a system and method improving the aerodynamics of the fan duct of a gas turbine engine and for reducing the weight of the fan duct components such that the performance of the engine may be improved. In addition, there exists a need in the art for a system and method for increasing the amount of fan duct wetted surface area that can be acoustically treated as a means for increasing the capacity for effecting noise reduction in the gas turbine engine.